US is not a democracy in a strict sense, it is more like plutocracy (people with money have the power).

  - the electoral college where winner takes all, so minority opposition vote is always suppressed
  - gerrymandering that dilutes and suppresses the minority opposition vote
  - oligopoly of two parties
  - unchecked financial influence by allowing unlimited funding via PACs
  - legalized lobbying/bribery
  - influence of special interest groups
  - the influence of legal system with expensive lawyers (that only rich can afford)